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Hi all. I plan on pulling the engine in my 68 442 to clean,fix leaks and paint it. My question is is it possible to get close to 400hp with c heads and without any major machine work? Maybe cam and springs? The car is all original(except paint, wheels and odds and ends), 74k. Its a 3 sp auto with i think 3:08 rear. I dont drive it hard so im not looking for hp at 6k+ lol
Have the heads professionally ported if you do not have the facility at home to do it. If your engine has the 1.99"/1.6" valves you can go to the 2.07"/1.68" valves and restore valve seat height and gain flow. Get a roller cam, it doesn't have to be too crazy. 220/230 on a wide LSA. .500" lift.
I would like more but it's not compatible with your 3.08 rear. Polish and enlarge the outlets of your W&Z manifolds - headers would be better but investigate the recessed
center exhaust port divider problem. You can weld up the heads or weld a tab on the headers to maintain separation. Zero deck the block. Balance the rotating and reciprocating assembly.
New rod bolts and resize the big end. Get a windage tray. A true 2 1/2" exhaust system to the mufflers; 2 1/4 tailpipes will be OK. 442 exhaust trumpets have small inlets but by the time the exhaust has got there it has cooled off a lot and won't make that much restriction. Look into the reproduction OAI systems put on the W30 cars. They were supposed to be worth 15-20 hp on the track if not on a dyno.
You're making a mistake concentrating on a particular HP number. The G-blocks were all about torque and any build on one should focus on that. All you're going to do with a lot of cam and carb is move the powerband up the RPM scale -- exactly what you don't want to do with these long-stroke engines. You'll just end up scattering the rods into the pan trying to buzz the thing up to six grand in search of your horsepower peak. I'm not saying there are no improvements to be had over the factory cam, but just be aware of the G-block's inherent limitations when selecting one.
If accepted for what it is, the G-block is a great motor and can be built to give you a pretty good kick in the ***.
@cutlassefi can usually be counted on for some pretty solid advice in this area. Make sure you give him an honest appraisal of your intentions for the build and your intended use of the car.
Ask one of the professional engine builders on this site for their opinion. I am not one of those but here is how I would approach the answer to your inquiry.
You are starting from a baseline of 325 SAE Gross rated horsepower when the engine was new. To convert that to today's rating methodology, used since the 72 model year, reduce the 325 number by maybe 15%. On these assumptions you are starting from no better than a 275 hp SAE Net baseline. I ballpark the gain from a set of new aftermarket aluminum heads out of the box at 50 horsepower which just gets you back to 325 SAE Net. From there you still have 75 hp to go. You do not want a high lift cam for your street use. I suspect this is why Android211 suggested that you go with a roller cam. A roller would require machine shop work. It still is not going to make up the 75 horsepower shortfall you would have even if you used aluminum heads.
You're making a mistake concentrating on a particular HP number. The G-blocks were all about torque and any build on one should focus on that. All you're going to do with a lot of cam and carb is move the powerband up the RPM scale -- exactly what you don't want to do with these long-stroke engines. You'll just end up scattering the rods into the pan trying to buzz the thing up to six grand in search of your horsepower peak. I'm not saying there are no improvements to be had over the factory cam, but just be aware of the G-block's inherent limitations when selecting one.
If accepted for what it is, the G-block is a great motor and can be built to give you a pretty good kick in the ***.
@cutlassefi can usually be counted on for some pretty solid advice in this area. Make sure you give him an honest appraisal of your intentions for the build and your intended use of the car.
X 2 Unless you dyno the engine, you won't know what HP level you got. Unless you post the dyno sheet on your car, no one will care or know what HP the engine makes. Don't get caught up in the numbers game. Drive and enjoy what you have. Maybe freshen it up if it needs it. Cutlassefi would be good for advice.
Set of new Edelbrock roller heads, milled to appropriate chamber volume for 9.5-10:1 CR with modern (thicker) head gaskets, once (if) they come available, paint them for unobtrusive appearance. Harland Sharp rockers, mild roller cam in the ballpark mentioned by Android except I would use more lift (.525-.550), long tube headers with 2 1/2” exhaust and either stock or aftermarket dual plane intake. You’ll likely be to your goal and torque should be impressive in a very usable power band on 91 or certainly 93 octane gas. A 3.42 - 3.73 gear swap would be huge and maybe a higher stall converter.
You’re biggest problem, other than burning $4-6k and keeping between the curbs when you give it the spurs might be constantly cleaning rubber shards off of your lower quarters.
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Last edited by bccan; October 26th, 2021 at 08:43 PM.
You need to fill the cyl in order to make tq. The 400G does that but at a low rpm. That's why it doesn't make any hp, it can't breathe in the higher ranges because of the smallish bore.
And not sure what the fascination is with "C" heads, they're really not any better than any other casting in that era, apples to apples.
Roller cams don’t require any additional machine work other than to cut the guides to accept more lift. But that would be required for any cam with lifts significantly more than stock.
Port the heads a bit or wait for the new Edelbrocks, shoot for a 10.0:1 real compression ratio, headers, a Performer intake and moderate cam and you should make an honest 375 or so on todays pump gas.
Let me know if I can be of help.
Thanks.
Last edited by cutlassefi; October 27th, 2021 at 04:17 AM.
Without getting into the engine and heads I think you will waste your time with a cam change.
In my opinion the biggest and easiest thing you could do for "seat of the pants" performance that you will notice would be to change the torque converter while you have the engine out. With the 3.08 rear I bet if you jumped up to around a 2000 rpm stall converter it would make a huge difference in how the car feels off the line.
First off, I am not an engine builder and have no words of wisdom in this area. That being said, I LIKE your paint! Very Sharp!!! Share some more pictures
First off, I am not an engine builder and have no words of wisdom in this area. That being said, I LIKE your paint! Very Sharp!!! Share some more pictures
And not sure what the fascination is with "C" heads, they're really not any better than any other casting in that era, apples to apples.
I think it's mainly because they're cheap and plentiful and have good valve sizes when compared to '70s smoggers like the "J" heads, for instance. I guess the flow characteristics probably aren't the ultimate, but for the inexpensive buy-in you can't have everything.
Last edited by BangScreech4-4-2; October 27th, 2021 at 02:34 PM.
Reason: TMI!
What would you guys recommend to wake this up a bit?
There's already a lot of good advice here from very knowledgable individuals. Unless you plan to drag race it, which you say that you don't, I would forget about trying to hit a specific HP number. That engine already makes a lot of torque (440 lb-ft at 3200) and for driving on the street, you may want to focus on taking advantage of all that torque with better gears (3.42 or more) and a higher stall torque converter. You don't have to go crazy with either to feel a difference.
I am also of the mindset of changing one thing at a time. You might find that changing the rear diff to a 3.42 or 3.73 is all that you needed to wake it up.
That said, I also see no harm in bolting on good long tube headers and switching to an Edelbrock Performer RPM air gap intake. Both of these would be useful if you decide to change cams or heads later on.
I think it's mainly because they're cheap and plentiful, have good valve sizes and yield decent compression when compared to '70s smoggers, like the "J" heads, for instance. I guess the flow characteristics probably aren't the ultimate, but for the inexpensive buy-in you can't have everything.
The combustion chambers and valves sizes are the same. The 71-up engines had lower compression ratio due to larger piston dishes.
And be ready for possibility of long delays getting parts in some cases. Machine work too…depending. I just finished 400g build and took 16 months due in large part to backlogged machine shops and shortages of cam cores and roller lifters.
That engine already makes a lot of torque (440 lb-ft at 3200) and for driving on the street, you may want to focus on taking advantage of all that torque with better gears (3.42 or more) and a higher stall torque converter. You don't have to go crazy with either to feel a difference.
I am also of the mindset of changing one thing at a time. You might find that changing the rear diff to a 3.42 or 3.73 is all that you needed to wake it up.
That said, I also see no harm in bolting on good long tube headers and switching to an Edelbrock Performer RPM air gap intake. Both of these would be useful if you decide to change cams or heads later on.
I agree with you and Bill regarding a gear change, but going from a 3.08 to a 3.42 would be noticeable, but not real significant. And he may not want to do a 3.73 without an overdrive.
The RPM wouldn’t be the correct intake for this application. The regular Performer would be a better choice.
I agree with you and Bill regarding a gear change, but going from a 3.08 to a 3.42 would be noticeable, but not real significant. And he may not want to do a 3.73 without an overdrive.
The RPM wouldn’t be the correct intake for this application. The regular Performer would be a better choice.
Of course you are absolutely right, Mark. My thought was to make incremental changes and no regrettable decisions. As you said, the 3.08 to 3.42 would not be a huge jump, I still think that he would be unlikely to regret having the 3.42 unless he is doing a lot of 70mph driving.
Regarding the Performer versus Performer RPM, you are certainly correct, but my reasoning was two-fold:
1) Where the RPM will give up some low end torque, if he changes to a higher stall converter, he might not spend much time in this range, but I am not clear on where in the powerband the RPM starts to outperform the Performer on a 400. Since the 400 makes so much torque, I thought that this might not be noticeable above the stall speed, but I definitely believe your recommendation.
2) The RPM would be a better long term choice if he does decide to change the cam or heads, but if it hurts the performance in the short term, he should definitely go with the Performer or just leave the stock intake.
Perhaps the cheapest performance gain could be derived from having your ignition timing recurved by someone with Olds engine experience. Unless you know a qualified person that is local, you would need to pull your distributor and send it out.
After 50 years a distributor can become tired and out of synch. A competent rebuild and recurve to factory specs isn't a bad idea but with a 10.5:1 nominal compression ratio I don't advocate an aggressive advance curve unless race gas is being considered. A complete tune up and new colder plugs wouldn't hurt.
. For the price a Performer isn't going to deliver the bang for the buck head porting and add roller cam are going to provide.
. I'm no expert. I've started porting a pair of B heads and there is a lot of room for improvement in those heads even for an amatuer like me.
Regarding the Performer versus Performer RPM, you are certainly correct, but my reasoning was two-fold:
1) Where the RPM will give up some low end torque, if he changes to a higher stall converter, he might not spend much time in this range, but I am not clear on where in the powerband the RPM starts to outperform the Performer on a 400. Since the 400 makes so much torque, I thought that this might not be noticeable above the stall speed, but I definitely believe your recommendation.
2) The RPM would be a better long term choice if he does decide to change the cam or heads, but if it hurts the performance in the short term, he should definitely go with the Performer or just leave the stock intake.
Thanks for the correction.
Thanks but I disagree. I've made as much as 540hp with a Performer on a 455. It's more than enough for a 400. no need for the RPM.
October 26th, 2021, 09:39 AM
